The present invention relates generally to computer networks and more particularly to a line powered control and switching device for selectively coupling a remote terminal at a remote location through modems and a telephone line to a local computer console terminal and a local CPU and which provides different degrees of access of the remote terminal and a variety of operating modes.
It is not uncommon for computer systems users to experience hardware, software or operational problems in the day-to-day use of their equipment. In some instances the problems are such that they can be diagnosed and/or corrected by on-site personnel; however, in most cases the user does not possess the technical skills needed to properly diagnose and then correct the fault. When this occurs it is generally necessary to obtain outside assistance from a technical expert at a support center.
In the past, attempts have been made to diagnose and correct operational problems by calling the support center over a telephone and describing to a technical expert at a support center what appears to be the particular problem. This technique has not proven to be very successful, mainly because of the inability of the person at the user site to accurately describe the problem and/or what he is actually observing on his display terminal. Furthermore, the technique does not enable the technical expert to actually control the operations of the computer at the user site.
Another technique that has been employed in the past has involved connecting the CPU and the display terminal at the user site to an acoustic coupler through a double throw switch. When the switch is placed in one position the CPU is connected to the display terminal and is operable with the display terminal as a user site computer. When the switch is placed in the other position the CPU is connected to the acoustic coupler. Using this arrangement it is possible to connect the CPU to either the display terminal at the user site or through a telephone link and second acoustic coupler to a display terminal at the support center. The basic problem with this technique is that although it allows either the display terminals as the user site or the display terminal at the support center to be connected to the CPU it does not allow both display terminals to be connected to and be in communication with the CPU at the same time. Thus, it does not enable a person at the support center to monitor operations of the display terminal at the user site or the operator at the user site to observe the communications between the display terminal at the support center and the CPU. In addition, once the telephone instruments at each location are inserted into their respective acoustic couplers there is no way for the person at one location to signal to the person at the other location to remove the telephone instrument from the acoustic coupler if the person wants to reestablish voice communications or return to the original operating mode.
In U.S. Pat. No. 4,356,545 to K. J. West there is described an apparatus for monitoring and/or controlling the operations of a computer at a user site from a support center over a telephone line, the computer at the user site including a central processing unit (CPU) and a display terminal. The apparatus includes a telephone instrument at each location connected to the telephone line, a display terminal connected to an acoustic coupler at the support center and a control and switching device at the user site connected to the CPU, to the display terminal at the user site and to an acoustic coupler. When a link is established between the acoustic coupler at the support center and the acoustic coupler at the user site over the telephone line, the display terminal at the support center is operable with the display terminal at the user site in either an on-line mode or a conversational mode. In the on-line mode, either display terminal can input to the CPU and the output from the CPU is displayed at both display terminals. In the conversational mode, the CPU is disengaged and inputs from either display terminal are displayed at both display terminals. In the absence of the link, the display terminal at the user site is operable with the CPU through the control and switching device.
It is an object of this invention to provide a new and improved control and switching device for allowing a remote terminal at a remote site to access a local system at a local site through modems over a telephone line.
It is another object of this invention to provide a control and switching device as described above which enables the remote terminal to access the local system for diagnostic and other purposes.
It is still another object of this invention to provide a control and switching device as described above which is microprocessor based.
It is yet still another object of this invention to provide a control and switching device as described above which is transparent to user software.
It is a further object of this invention to provide a control and switching device as described above which provides multiple degrees of access.
It is yet still a further object of this invention to provide a control and switching device as described above which does not use a framing error to cause a mode change.
It is another object of this invention to provide a control and switching device as described above which does not prevent communication between the local console and the CPU if power is down on the device.
It is still another object of this invention to provide a control and switching device which allows a remote terminal to access a local CPU either as a user or for diagnostic/maintenance purposes.
It is a further object of this invention to provide a control and switching device as described above wherein either the local computer console terminal or the remote terminal can be made master.
It is another object of this invention to provide a control and switching device as described above which is completely under control of the local console operator.